In a communication system that has been specified in the Third Generation Partnership Project (3GPP) such as Long Term Evolution (LTE) and LTE-Advanced (LTE-A), a terminal apparatus (User Equipment: UE) uses a Scheduling Request (SR) or a Buffer Status Report (BSR) to request a radio resource for transmitting uplink data to a base station apparatus (evolved Node B: eNodeB). The base station apparatus gives an uplink transmission allowance (UL Grant) to each terminal apparatus, based on the SR or the BSR. After reception of control information about the UL Grant from the base station apparatus, the terminal apparatus transmits uplink data on a prescribed radio resource, based on uplink transmission parameters included in the UL Grant.
In a case that the base station apparatus successfully receives the uplink data, the base station apparatus transmits a positive Acknowledgement (ACK) in downlink to the terminal apparatus after elapse of a prescribed time from receiving the uplink data. On the other hand, in a case of not successfully receiving the uplink data, the base station apparatus transmits a Negative Acknowledgement (NACK) to the terminal apparatus after elapse of a prescribed time from receiving the uplink data. The terminal apparatus receiving the NACK retransmits data associated with the uplink data. In this way, the base station apparatus controls all uplink data transmissions (data transmissions from the terminal apparatus to the base station apparatus). The base station apparatus controlling the uplink radio resource allows Orthogonal Multiple Access (OMA) to be realized.
The 3GPP has been specifying a radio access technology for realizing Massive Machine Type Communications (mMTC) as the fifth generation mobile communication system (5G) (NPL 1). In the mMTC, it is assumed that a large number of devices including the terminal apparatus and a sensor transmit and/or receive small data. For uplink mMTC, grant-free Non-Orthogonal Multiple Access (NOMA) has been discussed (NPL 2). The grant-free non-orthogonal multiple access permits that data transmitted from the terminal apparatuses the number of which exceeds the number of receive antennas of the base station apparatus is non-orthogonally multiplexed in space. In the grant-free non-orthogonal multiple access, the terminal apparatus transmits the uplink data to the base station apparatus without the SR transmission, the UL Grant reception, or the like. For this reason, in the grant-free non-orthogonal multiple access, even in the case that a large number of devices transmit and/or receive small size data, increase in overhead due to the control information can be suppressed. In the grant-free non-orthogonal multiple access, a time taken from generation to transmission of transmission data can be also shortened because the UL Grant reception and the like are not performed.